Laser cladding repair method for large-size defects of thin-walled cast aluminum alloy

Abstract

This invention discloses a laser cladding repair method for large-sized defects in thin-walled cast aluminum alloys, comprising the following steps: determining the defect area of ​​the cast aluminum alloy component to be repaired; determining a frustum-shaped region (wider at the top and narrower at the bottom) encompassing the defect area and removing the entire frustum-shaped region by cutting away; preparing a frustum-shaped compensation block of the same material as the cast aluminum alloy component to be repaired, and coaxially installing the compensation block into the cut frustum-shaped region for fixation, so that it forms an annular bevel region with a gradually decreasing width from top to bottom in the circumferential direction; using the annular bevel region as a filling area, using laser cladding equipment to fill the annular bevel region layer by layer to complete the defect repair of the cast aluminum alloy component; after repair, removing the fixture and machining the repaired area. This repair method can achieve low heat input, small filling volume, high-quality repair, high repair efficiency, and low repair cost.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy material repair, and specifically provides a laser cladding repair method for large-size defects in thin-walled cast aluminum alloys. Background Technology

[0002] Aluminum alloys are widely used in aerospace, rail transportation, and other fields. Casting technology, with its advantages of low cost and fast forming, has played a vital role in promoting the engineering application of aluminum alloys. However, aluminum alloys prepared by casting are prone to metallurgical defects such as porosity and shrinkage porosity in local components. This is especially true for cast aluminum alloy components with complex thin-walled structures or local thin-walled structural features, where defects are more likely to occur. These defects can range from compromising component quality to rendering parts unusable. Repairing these defects through welding, cladding, and other methods is a common approach.

[0003] Laser cladding is an advanced defect repair technology. In recent years, its application in the repair of cast aluminum alloys has become increasingly widespread, attracting attention due to its advantages such as high repair precision and good bonding strength. Traditional laser cladding repair involves machining the defect and its surrounding area before using laser cladding for repair. However, for large defects with thin-walled structures, although laser cladding has lower heat input, the prolonged, large-area continuous cladding process can lead to heat accumulation, causing deformation of the component during repair and severely affecting repair quality. Furthermore, cladding materials are often expensive, so completely filling the defect area in this way also increases repair costs. These issues severely restrict the further promotion of laser cladding technology in the repair of dimensional defects in cast aluminum alloys.

[0004] Therefore, for large-sized defects in thin-walled cast aluminum alloys, how to significantly reduce the amount of laser cladding material and the heat input while ensuring repair quality, thereby reducing costs and improving repair efficiency, has become an urgent problem to be solved. Summary of the Invention

[0005] In view of this, the present invention provides a laser cladding repair method for large-size defects in thin-walled cast aluminum alloys. By designing and adding compensation blocks of specific shapes and sizes and combining them with laser cladding, large-size defects in thin-walled cast aluminum alloys can be repaired, thereby solving the problems of poor repair quality, low repair efficiency and high repair cost in the prior art.

[0006] This invention provides a laser cladding repair method for large-size defects in thin-walled cast aluminum alloys, comprising the following steps:

[0007] Determine the extent of the defect area in the cast aluminum alloy component to be repaired;

[0008] Define a frustum region D that is wider at the top and narrower at the bottom, containing the defective area, and cut away the entire frustum region;

[0009] Prepare a frustum-shaped compensation block of the same material as the cast aluminum alloy component to be repaired, and coaxially install the compensation block into the cut frustum area for fixation, so that it forms an annular bevel area with a width that gradually decreases from top to bottom in the circumferential direction with the frustum area. The thickness of the compensation block is greater than the thickness of the defect area of ​​the cast aluminum alloy component to be repaired, and the diameter of the large end of the compensation block is greater than the diameter of the small end D of the frustum area.

[0010] Using the annular bevel area as the filling area, laser cladding equipment is used to fill the annular bevel area layer by layer to complete the defect repair of the cast aluminum alloy component;

[0011] After the repair is completed, the clamps are removed and the repaired area is machined.

[0012] Preferably, the method for determining the frustum-shaped region D, which is wider at the top and narrower at the bottom and includes the defective region, is as follows:

[0013] Determine the longest diameter d within the defect area and use this diameter as the baseline segment;

[0014] The baseline segment is translated upwards until it is tangent to the upper boundary of the defect area; then, the upwardly translated segment is extended to both ends to obtain segment ab.

[0015] The baseline segment is translated downwards until it is tangent to the lower boundary of the defect area. The resulting segment after downward translation is denoted as segment cd.

[0016] Draw two circles, one centered at the midpoint of line segment ab and the other at half the length of line segment cd, with the other half as the radius.

[0017] Using two circles as the upper and lower boundaries, an inclined cut is made along the edges of the two circles to form a frustum region D that is wider at the top and narrower at the bottom.

[0018] Further optimization involves making the length of line segment ab 2-4 mm greater than the longest diameter d.

[0019] Further preferably, the thickness of the compensation block is the thickness H of the defect area of ​​the cast aluminum alloy component plus (3~5mm); the diameter of the upper bottom surface of the compensation block is C1=2Ra-(1~2mm), and the diameter of the lower bottom surface is C2=2Rc+(1~2mm).

[0020] Further optimization involves filling the annular bevel area layer by layer from bottom to top with laser cladding. When the bevel area width W ≤ the spot diameter Φ, single-pass laser cladding is performed along the intersection line L of the side of the compensation block and the cutting surface of the cast aluminum alloy component. When the bevel area width W > the spot diameter Φ, a multi-pass overlapping laser cladding process is adopted.

[0021] Further optimization involves ensuring that the endpoint overlaps with the starting point by 5-10 mm during each laser cladding process.

[0022] Further preferably, before laser cladding, the process includes a step of cleaning the cutting surface of the cast aluminum alloy component and the side surface of the compensation block.

[0023] Further preferably, the machining process includes: removing the height allowance reserved by the compensation block by milling or grinding; grinding the weld bevel area and heat-affected zone to remove burrs and oxide scale.

[0024] The laser cladding repair method for large-size defects in thin-walled cast aluminum alloys provided by this invention adopts a geometrically adapted laser cladding repair technology. By determining the geometric characteristics of the defect area, a frustum-shaped cutting and compensation block adaptation design are adopted, combined with a multi-pass laser cladding process. Taking advantage of the high energy density of the laser, aluminum-based powder is filled into the annular bevel area formed between the compensation block and the area to be repaired. Under an argon-protected environment, low heat input, small filling amount, high-quality repair can be achieved, with high repair efficiency and low repair cost. Attached Figure Description

[0025] Figure 1 This is a schematic diagram showing the location of the cast aluminum alloy component to be repaired, the compensation block, and the annular bevel area during the laser cladding repair process in an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram showing the location of the frustum region to be cut in an embodiment of the present invention. Detailed Implementation

[0027] To better explain and facilitate understanding of the present invention, the technical solution and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] See Figure 1 , Figure 2 This invention provides a laser cladding repair method for large-size defects in thin-walled cast aluminum alloys, comprising the following steps:

[0029] (1) Determine the extent of the defect area of ​​the cast aluminum alloy component 1 to be repaired;

[0030] Non-destructive testing methods such as X-ray flaw detection or ultrasonic testing are used to inspect the cast aluminum alloy component 1 to be repaired, analyze the specific size, spatial location and geometric shape of metallurgical defects such as porosity and shrinkage caused by the casting process, and determine the range of defect areas that need to be treated later.

[0031] (2) Determine a frustum region D that is wider at the top and narrower at the bottom, including the defective region, and cut away the entire frustum region;

[0032] The method for determining the frustum-shaped region D, which is wider at the top and narrower at the bottom and includes the defective region, is as follows:

[0033] (21) Determine the longest diameter d within the defect area and use this diameter as the baseline segment;

[0034] (22) The reference line segment is translated upward to be tangent to the upper boundary of the defect area; then, the line segment after upward translation is extended to both ends to obtain line segment ab. Preferably, the length of line segment ab is 2 to 4 mm larger than the longest diameter d.

[0035] (23) The baseline segment is translated downwards until it is tangent to the lower boundary of the defect area. The resulting line segment after downward translation is denoted as line segment cd.

[0036] (24) Draw two circles with the midpoints of line segments ab and cd as the centers (denoted as center A and center C respectively) and the half lengths of line segments ab and cd as the radii (denoted as Ra and Rc respectively);

[0037] (25) Using the two circles as the upper and lower boundaries, perform inclined cutting along the edges of the two circles, so that the side surface formed by the cutting smoothly transitions downward from the edge of the circle containing the center A to the edge of the circle containing the center C, forming a frustum region D that is wider at the top and narrower at the bottom (e.g. Figure 1 (as shown)

[0038] (3) Prepare a frustum-shaped compensation block 2 of the same material as the cast aluminum alloy component 1 to be repaired, and coaxially install the compensation block 2 into the cut frustum area for fixation, so that it forms an annular bevel area 3 with the frustum area in the circumferential direction whose width gradually decreases from top to bottom. This annular bevel area is the filling space for subsequent laser cladding (e.g., Figure 1As shown in the figure, the thickness of the compensation block is greater than the thickness of the defect area of ​​the cast aluminum alloy component to be repaired, and the diameter of the large end of the compensation block is greater than the length of the line segment cd. When installed, the large end of the compensation block faces down and the small end faces up, and it is coaxially installed into the frustum area from the lower direction of the cast aluminum alloy component until the compensation block can no longer move upward, that is, the two are tightly fitted; preferably, the thickness of the compensation block is the thickness H of the defect area of ​​the cast aluminum alloy component + (3~5mm); the diameter of the upper bottom surface of the compensation block C1 = 2Ra - (1~2mm), and the diameter of the lower bottom surface C2 = 2Rc + (1~2mm); the size design ensures the geometric fit between the compensation block and the frustum area D, providing a structural basis for the accurate formation of the bevel area; wherein, the compensation block can be fixed by an adjustable mechanical clamp, the gap between the two is ≤0.05mm, and the coaxiality between the two is ≤0.1mm;

[0039] (4) Using the annular bevel area as the filling area, the annular bevel area is filled layer by layer with laser cladding equipment to complete the defect repair of the cast aluminum alloy component;

[0040] In this process, laser cladding fills the bevel section layer by layer from bottom to top. As the filling height increases, the width of the area to be filled gradually increases. When the bevel area width W ≤ the spot diameter Φ, single-pass laser cladding is performed along the intersection line L of the side of the compensation block and the cutting surface of the cast aluminum alloy component. When the bevel area width W > the spot diameter Φ, a multi-pass overlapping laser cladding process is adopted. The overlap width of adjacent weld passes is denoted as Y. During repair, a heat-affected zone of Φ / 5 is reserved on both sides of the width direction. The single-sided width shrinkage amount is... , width of the i-th cladding layer Effective cladding width Number of repairs for the i-th layer Total number of floors The overlap width of two adjacent cladding channels Where W0 is the top width of the bevel, Wn is the bottom width of the bevel, E is the total number of layers, η is the overlap ratio, ηz is the interlayer compression ratio, ΔW is the width shrinkage on one side, and h is the forming height of a single layer. It is a rounding function;

[0041] Preferably, the repair process starts from the starting point along the intersection line L and forms a closed loop at the starting point, with the end point of the loop overlapping the starting point by 5~10mm to avoid incomplete fusion at the endpoints;

[0042] Further optimization involves using an 800-2000W fiber laser with a spot diameter of 0.8-2mm for laser cladding repair; using aluminum-based powder that has been dried at 100℃ for 2 hours; a powder feeding rate of 8-15g / min; and an argon powder feeding flow rate of 8-12L / min; with high-purity argon protection (main gas 15-20L / min, side gas 5-8L / min).

[0043] In addition, before laser cladding, the cutting surface of the cast aluminum alloy component and the side of the compensation block are cleaned to remove surface dust and oil. The cleaning can be performed before or after fixing the compensation block.

[0044] (5) After the repair is completed, remove the fixture and machine the repair area. Use milling or grinding to remove the height allowance reserved by the compensation block so that the surface of the repair area is flush with the surface of the substrate. Grind the cladding bevel area and heat-affected zone to remove burrs and oxide scale, and ensure that the surface roughness of the repair area is consistent with that of the substrate.

[0045] Example 1

[0046] The object to be repaired is a ZL104 thin plate with a thickness of 3mm. X-ray flaw detection was used for non-destructive testing to determine the specific size, spatial location and geometry of metallurgical defects such as porosity and shrinkage caused by the casting process, and to determine the range of defect areas that need to be treated later.

[0047] Determine the longest diameter of the defect area as d = 8mm. Use this diameter as the baseline segment. Translate the baseline segment upwards until it is tangent to the upper boundary of the defect area, with segment ab = 10mm. Translate the baseline segment downwards until it is tangent to the lower boundary of the defect area, with segment cd = 8mm. Take the midpoints of ab and cd respectively (denoted as center A and center C). Draw two circles with radii Ra = 5mm and Rc = 4mm, respectively, using these two circles as the upper and lower boundaries. Perform inclined cutting along the edges of the two circles so that the side formed by the cutting smoothly transitions from the edge of the circle containing center A to the edge of the circle containing center C, forming a frustum region D that is wider at the top and narrower at the bottom. Finally, cut away the frustum-shaped defect area.

[0048] 104 aluminum alloy was selected as the material for the compensation block. The thickness of the defect area was H=3mm, the thickness of the compensation block was set to 6mm, the diameter of the upper bottom surface of the compensation block was C1=8mm, the diameter of the lower bottom surface was C2=10mm, and the side surface of the compensation block and the cutting surface were used as the welding mating surface.

[0049] After the two are tightly fitted together, an annular bevel area with an upper W=2.20mm, a bottom angle of 40.24°, and an inverted triangular cross-section is formed. Dust and oil are removed from the cutting surface of the cast aluminum alloy material and the side of the compensation block. An adjustable mechanical clamp is used to fix the compensation block from bottom to top. The fit gap between the cutting surface of the cast aluminum alloy material and the side of the compensation block is confirmed to be 0.03mm, and the coaxiality between the two is 0.05mm, which meets the requirements of small fit gap and high coaxiality. After fixing, the clamp pressure is kept stable until the laser cladding is completed.

[0050] An 800W fiber laser and a 1.2mm spot diameter laser cladding equipment were selected. Al-Si alloy powder was used as the cladding material, dried at 100℃ for 2 hours, with a powder feed rate of 10g / min and an argon powder feed flow rate of 10L / min. High-purity argon gas protection was used, with a main gas flow rate of 18L / min and a side gas flow rate of 6L / min. In the initial stage of cladding, W was smaller than the laser diameter, and single-pass laser cladding was performed in the bevel area. When the cladding height reached 1.6mm, the bevel width W=1.3mm was larger than the laser diameter, and a multi-pass overlapping laser cladding process was adopted. During welding, a heat-affected zone of 0.24mm was reserved on both sides in the width direction. In the repair of two adjacent passes, the overlap width between the repair width of the later repair and the previous repair was 0.48.

[0051] After the repair is completed, the fixture is removed, and the repaired area is machined. The 6mm height allowance reserved by the compensation block is removed by milling to make the surface of the repaired area flush with the surface of the substrate. The cladding bevel area and heat-affected zone are ground to remove burrs and oxide scale, ensuring that the surface roughness is consistent with the substrate.

[0052] Example 2

[0053] The method is the same as in Example 1, except that:

[0054] (1) The material to be repaired is ZL102 thin plate; the thickness of the thin plate is 2mm, and Al-Si alloy powder is used for repair. The longest diameter of the defect is d=20mm, ab=22mm, cd=20mm. The frustum cut out has Ra=11mm, Rc=10mm and height h=2mm.

[0055] (2) The height of the compensation block is H=4mm, C1=17mm, and C2=21mm;

[0056] (3) Laser spot diameter Φ=0.8mm, bevel top width W=2.00mm (>Φ), overlap rate η=0.4, total number of layers E=2, number of passes per layer N1=3, N2=4;

[0057] (4) 1200W fiber laser, spot diameter 0.8mm, powder feed rate 12g / min, high-purity argon protection, main gas 17L / min, side gas 5L / min.

[0058] The samples obtained in Examples 1 and 2 were tested and found that the porosity of the repaired area was significantly lower than that of the traditional full cladding filling method; the deformation of the component was at a low level; the performance of the repaired area was close to that of the substrate, the hardness of the repaired area reached more than 90% of that of the substrate, and the corrosion resistance was comparable to that of the substrate.

[0059] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0060] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method of laser cladding repair of large size defects in thin-walled cast aluminum alloy, characterized in that, Includes the following steps: Determine the extent of the defect area in the cast aluminum alloy component to be repaired; Define a frustum region D that is wider at the top and narrower at the bottom, containing the defective area, and cut away the entire frustum region; Prepare a frustum-shaped compensation block of the same material as the cast aluminum alloy component to be repaired, and coaxially install the compensation block into the cut frustum area for fixation, so that it forms an annular bevel area with a width that gradually decreases from top to bottom in the circumferential direction with the frustum area. The thickness of the compensation block is greater than the thickness of the defect area of ​​the cast aluminum alloy component to be repaired, and the diameter of the large end of the compensation block is greater than the diameter of the small end D of the frustum area. Using the annular bevel area as the filling area, laser cladding equipment is used to fill the annular bevel area layer by layer to complete the defect repair of the cast aluminum alloy component; After the repair is completed, the clamps are removed and the repaired area is machined.

2. The method of claim 1, wherein the laser cladding repair of large size defects in thin-walled cast aluminum alloy is characterized by: The method for determining the frustum-shaped region D, which is wider at the top and narrower at the bottom and includes the defective region, is as follows: Determine the longest diameter d within the defect area and use this diameter as the baseline segment; The baseline segment is translated upwards until it is tangent to the upper boundary of the defect area; then, the upwardly translated segment is extended to both ends to obtain segment ab. The baseline segment is translated downwards until it is tangent to the lower boundary of the defect area. The resulting segment after downward translation is denoted as segment cd. Draw two circles, one centered at the midpoint of line segment ab and the other at half the length of line segment cd, with the other half as the radius. Using two circles as the upper and lower boundaries, an inclined cut is made along the edges of the two circles to form a frustum region D that is wider at the top and narrower at the bottom.

3. The laser cladding repair method for large-size defects in thin-walled cast aluminum alloys according to claim 2, characterized in that: The length of line segment ab is 2-4 mm greater than the longest diameter d.

4. The laser cladding repair method for large-size defects in thin-walled cast aluminum alloys according to claim 1, characterized in that: The thickness of the compensation block is the thickness H of the defect area of ​​the cast aluminum alloy component + (3~5mm); the diameter of the upper bottom surface of the compensation block is C1 = 2Ra - (1~2mm), and the diameter of the lower bottom surface is C2 = 2Rc + (1~2mm).

5. The method of claim 1, wherein the laser cladding repair of large size defects in thin-walled cast aluminum alloy is characterized by: Laser cladding is performed by filling the annular bevel area layer by layer from bottom to top. When the bevel area width W ≤ the spot diameter Φ, single-pass laser cladding is performed along the intersection line L of the side of the compensation block and the cutting surface of the cast aluminum alloy component. When the bevel area width W > the spot diameter Φ, a multi-pass overlapping laser cladding process is adopted.

6. The method of claim 1, wherein the laser cladding repair of large size defects in thin-walled cast aluminum alloy is characterized by: During each laser cladding process, the endpoint overlaps with the starting point by 5~10mm.

7. The laser cladding repair method for large-size defects in thin-walled cast aluminum alloys according to claim 1, characterized in that: The process before laser cladding also includes cleaning the cutting surfaces of the cast aluminum alloy component and the sides of the compensation block.

8. The method of claim 1, wherein the laser cladding repair of large size defects in thin-walled cast aluminum alloy is characterized by: The machining process includes: removing the height allowance reserved by the compensation block by milling or grinding; grinding the weld bevel area and heat-affected zone to remove burrs and oxide scale.

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